Telephone system



APHl 18, 1944 K. L.. FREDERICK TELEPHONE SYSTEM Filed June so, 1942 5 sheets-sheet 1 WEA/ron Bf/(LFREDER/CK WW-Www ATTORNEY April 18, 1944. K'. L. 'FREDERICK 2,346,915

TELEPHONE SYSTEM 5 sheets-Sheet 2 Filed June 30, 1942 /A/l/NTOR KLfREDER/CK 'MW/m4 u v Y my 5 Afro April 18, 1944v K. L. FREDERICK TELEPHONE SYSTEM Filed June 3o, 1942 Q S V 5 sheets-sneu s /Nl/ENTOR KLFREDER/CK BV ATTORNEV April 18, 1944.

K. L.. FREDERICK TELEPHONE SYSTEM Filed June so, 1942 5' sheets-sheet 4 Il IIII /NVENTOR f/ fREOER/CK Arron/wy April 18, 1944 K. L. FREDERICK 2,346,915

TELEPHONE SYSTEM Filed June 30, 1942 -5 Sheets-Sheet 5 IHI IIII llll Illll INI I I I |f.l

/Nl/E/VTOR KLFREDER/CK @yew . ATTORNEY Patented Apr. 18, 1944 TELEPHONE SYSTEM Kenneth L. Frederick, Berwyn, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application June 30, 1942, Serial No. 449,083

7 Claims.

This invention relates to telephone systems and particularly to automatic telephone systems in which connections are established by means of crossbar switches.

An object is to simplify automatic telephone systems of this kind in which a small number of subscribers lines :are involved, such as private branch exchange systems.

Heretofore such systems have been arranged in which single crossbar switches served both as line iinders and as connectors, that is, a connection between a calling subscriber and a called subscriber may be made by the establishing of a connection through a line finder section from the calling line to one end of a link, and when the calling subscriber dials the number of the called subscriber, the connector section operates to complete a connection from the other end of this link to the called line.

The applicants invention has been applied to a system of this kind and relates particularly to the line-finder section of the system. The special arrangement in which the features of the appli cants invention appear is such that trunks or outgoing links from the line-iinder section are arranged in pairs on the horizontals while incoming links are arranged in pairs on the verticals in the line-finder crossbar switches. Each outgoing link in each pair has access to a corresponding incoming link in each pair and each subscribers line has access to a separate pair of said incoming links. These incoming links, of course, also appear in the connector section of the crossbar switches. The general arrangement of the system to which the connection has been applied is such that the calling subscriber will establish a connection through :an incoming link to an outgoing link in the line-iinder section, and this outgoing link extends through other selector switches and mechanisms through which a,v connection is established to a trunk terminating in the connector section where a connection is established from this trunk through one of the pair of vertical incoming links to a called subscribers line.

A feature of the invention resides in a busy test controlarrangement for establishing a connection between a calling line and one of the idle outgoing links over a vertical incoming link and the arrangement is such that when a subscriber calls a rst pair of outgoing links are chosen of which one at least is idle and the iirst idle link of this pair is then chosen for connection to the subscriber over a corresponding vertical link, that'is, the idle link determines whch`ver`55 tical link shall be used and the pair of links of which this idle link is one determines which cross-connection shall be used to connect the idle link to .the corresponding vertical link.

The arrangement has been illustrated in the accompanying drawings, in which:

Fig. 1 shows in general and in diagrammatic form a switching plan of a private'branch exchange system in which the applicants invention has been incorporated; l

Figs. 2, 3 and 4 arranged in accordance with Fig. 5 illustrate in general the trunking and linking arrangement foran exchange of a capacity of 10o lines, and Figs. 6 and .7 arranged with Fig. 6 above Fig. 7, show a section of a line-finder connector switch vin which one subscribers line terminates and the associated circuits and mech.- anism embodying the applicants invention.

Referring now to the drawings, and particularly to Fig. 1, the private branch exchange illustrated may consistof, in general, a group oi lineiinder and connector switches shown at l in which subscribersV lines indicated at 2 and ten trunks indicated at 3 may terminate and from the line-finder sections, outgoinglinks, such as 4,.-may extend to a selector switch 5, back to an incoming trunk arrangement 6 to the connector sections of the switches I. When a subscriber or trunk in group 2 or 3 calls, an outgoing link in the line-finder section of the group 4 is chosen and the connection is extended through this 1ine' finder section to the selector'5. yThe callingsubscriber or trunk may then dial two digits. The first digit will operate the selector switch to iind a trunk in the group 6 that extends to aparticular group of subscribers lines in which the called subscribers line is lone, then a second digit is dialed and the chosen trunk is the'n connected to the called subscribers line. This may be accomplished in any'well-known manner through registers and other mechanisms well known in the art for selecting links and trunks through crossbar switches and need not be illustrated or described in detail as the applicants invention is not concerned with the general plan; The only reason why this brief description is made 'ofl the system is tok clearly place the applicant's'invention in the art.

If this hundred-line capacity exchange is considered, the general wiring plan has Vbeen outlined in Figs. 2, 3 and 4. It is understood thatthe various -circuits are here merely representedv by single conductors and the contacts at the crosspoints of the switches are merely represented 4by a single contactv for the sake of simplicity and clearness. Considering the line-finder connectors, these switches may be divided in five units with the connector sections marked IU to I4 and with the line-nder sections marked I5 to IS. Each unit serves a group of twenty subscribers lines, the lines being marked lines I to 20, 2|, 40, 4I to G0, -6| to 80, and 8| to Iil, respectively, in the five units. In each groupk of twenty lines, each line has access to a separate pair of vertical incoming links such as 25 and 2| in the connector section IU for line I. Each of the vertical links ofy each twenty pairs in a line-iinder section has access at three crosspoints to any one of three separate outgoing links. That is, the left-hand vertical links of each pair of the twenty pairs in the rst line-finder section I5 have access to links 22, 23 and 24 and the companion links have access to the three links 25, 25 and 21. This will provide, therefore, for the live units, a

group of thirty links outgoing from the line-finder sections I5 to I8. By these means, therefore, any one of the twenty subscribers in any group has access to six outgoing links by first establishing a connection to one 01 the other of the vertical links to choose a group of three links, and connect this vertical link to one of .the three chosen links. These thirty outgoing links are then connected at 30 to two groups of five trunks each in any suitable cross-connecting manner so that, for example, the fteen odd-numbered links are cross-connected with three links to one of the live trunks in the group and the fifteen even links are cross-connected with three links to one of the trunks in the other group. These ten trunks are then connected to appear in ten verticals in ten succeeding sections of the selector switch 32. For example, in section 33 the trunk 34 is connected to the vertical link 35. Each vertical link in the tens section has access to ve outgoing trunks at ten crosspoints, for example, link 35 has access to ve trunks 35, thus fifty trunks extend from the selector 32 to the connector sections I0 to I4 of the line-nder connector. These fifty outgoing trunks are then divided in groups of ten,

. each group appearing in a separate level in the connector sections so that these connector ,sections are provided for that purpose with ve levels of contacts, that is, a pair of incoming trunks one from each of two adjacent groups of ve has access to twenty subscribers lines in a corresponding level with one trunk of a pair having access to one of each pair of vertical links and the other having access to the other one of each pair of vertical links in the group of forty having access to twenty subscribers lines. For example, the outgoing'V trunk 38 of group 35 has access to vertical link 20 of line I and the corresponding vertical links of the other nineteen subscribers lines in section Il), while link 40 of group III has access to vertical link 2l of line I and the corresponding vertical links of the other nineteen subscribers lines in section I0. Thus, the groups of links 36 and il have access to the first level of sections I0 to I4 and correspondingly the other groups of trunks have access to the other four levels.

In general, therefore, if a connection is desired by the subscriber of line I to the subscriber of line 20, the operation would be as follows. The subscriber of line I in seizing his line causes operations to take place as will be described in detail hereinafter to establish a connection to an idle outgoing link of the six links 22 to 21 in the line-under section I5 by rst determining whether there is an idle link available in the 75 rst pair of links 22 and 25 or if the rst pair is busy in the second pail` 23 and 24 and if the second pair is busy in the third pair 24 and 21. Thus the first pair in which a link is idle will then be preselected. It is then determined Whether a first or a second link in the chosen pair is idle, that is, for example, if the first pair 22 and 25 has been preselected, and the link 22 is idle, connection would be established to this link over a corresponding vertical link 20, the vertical link 20 being also chosen at that time to establish a connection to the subscriber I at contacts which will be closed due to the fact that the vertical link 2i] was chosen. These selecting operations are performed in accordance with applicants invention which will be described in detail in connection with Figs. 6 and '1 hereinafter. For the present the connection from this chosen link to the subscribers line 2li will be described in general. Consider then that after the link 22 has been chosen, it would follow that this link will be connected over the link 34 to the verticals 35 in Fig. 33 of the selector 32. The subscriber will now dial two digits, for example, 2 and (l. Digit 2 will operate the selector 32 to establish a connection at the crosspoint 46 between vertical 35 and trunk 33 in section 33. This, of course, determines that a subscriber in the first group of twenty is desired as link 33 has access to this group and also the choice of link 38 determines that a left-hand vertical link in the connector sece tion I0 shall be used by the operation of contacts 41. Now all that remains is to dial digit 1. This causes the connector section I0 to be operated to establish a connection between link 38 at crosspoint 49 with the subscribers line 2U through the connection at 41.

All of these operations in the selector switch 32 and the connector section I0 do not form part of the applicants invention so that further detailed descriptions appear to be unnecessary. On the other hand, the part of this switching system to which applicants arrangement has been applied will now be described in detail in connection with Figs. 6 and '1 Where one subscribers line has been shown with the necessary detail circuits for the establishing of connections from this line to one of the six links to which it has access in the line-under section. It should be noted that the subscribers line I is incoming to the connector section IIJ and terminates in the twovertical links 2E! and 2l and may be connected through contacts at the crosspoint 45 to link 20 by the operation of the primary select magnet 5U or through contacts at the crosspoint 5I to link 2i by the operation of the primary select magnet 52 followed in either case by the operation of the usual hold magnet 53. The hold magnet 53 serves, of course, also for connecting either one of these two links to one of the six outgoing links 22 to 21 through three groups of contacts at the crosspoints 55, 5S and 51. The select magnets for these three crosspoints are marked 58, 59 and 60, respectively, in the linefinder section I5. The hold magnet 53 also serves for .connecting any one of the ten trunks incoming to a connector section ID from the selector 32 with the aid, of course, of the select magnets 62, G3, 64, or 66 to establish connections at the crosspoints 61, 68, 69, 10 or 1I in the general manner as described hereinbefore.

If it is assumed then that the subscriber of line I calls, the establishing of this connection causes the operation of relay 89 from battery, a Winding of relay .80 through contacts of relay 8l over the tip and ring conductors through the calling subscribers loop, contacts of relay 8|, another winding of relay 88, to ground at contacts of relay 83. Relay 88 in operating provides a locking circuit for itself through its righthandA armature and front contact to ground, independent of the ground supplied at contacts of relay 83 and closes an obvious circuit for the operation of relay 83. An idle outgoing link will now be selected. As hereinbefore stated, it Will rst be determined Whether a link is idle in the first group of two, that is, links 22 and 25 controlled by contacts at the crosspoint 55 or in the second group of two, that is, links 23 and 25 controlled by contacts at crosspoint 56 or in the third group of two, that is, links 2A and 21 controlled by the contacts at the crosspoint 51. If onevof the links in the iirst group is idle, for example, link 22, it Will be noted that the linkbusy relay 98 for this link is not operated.' Consequently, on the operation of relay 83 a circuit is completed for the operation of the select magnet 58 which controls the contacts at the crosspoint 55. This circuit may be traced from battery through contacts of relay 83, contacts of select magnets 52 to 65 in the connector section, contacts of busy relay 88, Winding of select magnet 58 to ground. Another circuit is simultaneously closed for the operation of the vertical link select magnet 58 from battery, contacts of relay 83 and the select magnets as hereinbefore traced through contacts of relay 98, Winding of select magnet 58 to ground. On the operation of the select magnet 58 a circuit will be closed for the hold magnet 53 from battery through the Winding of this magnet, contacts of relay 88 and contacts of select magnet 58 to ground, thus causing a connection to be established at the crosspoint 55 from the subscribers line I through contacts at the crosspoint 45 controlled by the select magnet 58, the vertical link 28, contacts at the crosspoint 55 to the conductors of link 22. A connection from ground will now be established from the sleeve lead of link 22, contacts at crosspoints 55 and A5, winding of the cut-01T relay Bi to battery causing the operation of this relay which in operating closes an obvious locking circuit for the hold magnet 53 and opens the connections for relay 88 which release causing the release of relay 83, the select magnets 58 and 58. The busy relay 95 will now also operate from battery through the Winding of this relay t the same ground over the sleeve lead of link 22 to hold this link busy. The fact, l

therefore, that the busy relay S8 was not operated when the call was made determines that the link 22 of the rst pair 22 and 25 was idle. Had this relay been operated, and had the other link 25 of this pair been idle, the fact that the busy relay 98 for this link 25 was not operated, Would have determined that the connection should be established to this link 25 instead. If this had been the case when relay 83 operated, the circuit traced from battery, contacts of relay 83 and the select magnets of the connector section |8 would have extended through contacts of the actuated busy relay 98, contacts of released busy relay 88 and winding of the same select magnet 58 and cause the operation of this magnet, but instead of select magnet 53 being operated at this time, the select magnet 52 would operate simultaneously with the select magnet 58 over the circuit from the battery at relay 83 through the contacts ofthe select magnets in the, connector. .section I8,

operated contacts-of relay 9D, contacts of released relay 98, Winding of select magnet 52 to ground. Consequently, when the select magnet- 52 operates, the subscribers line will in this case be connected through contactsA at crosspoint 5| controlled bythe select magnet 52, link 2|,contacts at crosspoint 55 to link 25. When this connection is made the busy relay 98 will operate from battery. overthe sleeve of link 25 to ground. Thus it will be seen that if either one or both. of links 22 or 25 are idlethe connection Would'be. extended over one or the'other of these links, provided that if the rst link 22 were4 idle, this link would be chosen for the connection, and if `the link25 only were idle, this link25-Would be used for the connection. If both links 22 and 25 are busy, both relays 98 and 98 will beoperated and the choice of an idle trunk would be madeA in thesecond pair 23 and 26 and similarly Va choiceof a rst'idle one of this pair would be chosen` iorathe connection. For example, if link 23 were idle, busy relay |83 will be in released condition. In this case as busy relays 98 and 98 are operated, the select magnet 59 Will operate over the circuit at the con..

tacts ,of relay 83 through the contacts of the select magnets in the connector section, contacts of operated busy relays 98 and 98 and contacts of busy relay |83, winding of select magnet 59 to ground.l The select magnet v58 would also operate tor choose the Vertical link 28. On the other hand, if link 23 is busy and link 28 is idle, the select magnet 59 willv operate as before but due to the fact that relay |83 is now operated, the select magnet 52 will operate instead ofthe select magnet 58 to extend the connections overl link 2|.rv Similarly, if. the rstvfour links are busy, an idle trunkof the pair 24 and 21 Will be chosen and always a rst idle link of the pair.

It is, therefore, seen that With the applicants invention as applied to this kind of system, the idle outgoing links will be chosen in a certain order. That is, rst it is determined Whether there is an idle link in the first, second or third pair. It' an idle trunk exists in the first pair it is determined Whether a first or a second link in this chosen pair is idle. If the first link is busy the second link will be chosen. If both links in the first pair are busy, the first idle link in the next pair, will b e chosen, etc. This choice of an idle link is determined by the six busy link relays 98, 88, |83,.|88, |88 and H8. Each one of these busy relays Will also determine which vertical link is to be employed in establishing a connection through the line-finder section to the linkf chos-en from the calling subscriber. That is,v for example, relay l98 Will v determine that select magnet 58 will be operated to select vertical` link v25 and relay 98 Will determine that the select magnet 52 Will be operated to choose vertical link 2|, etc. This .arrangement enables a pair of links tobe terminated at a single crosspoint in each line-finder section and a common set of six link-busy relays may be employed for the establishing of lconnections for twenty subscribers with six links.

What is claimed is:

l. In a telephone system, a crossbar lswitch having intersecting horizontal and vertical rows o'f contacts, pairs of trunks, each pair terminating in a separate horizontal row of contacts. pairs of links, each pair terminating in a separate vertical row of contacts, said horizontal and vertical rows of contacts at each intersecting point beingl arranged to establisha connection between one trunk and one link of the two in'-` tersecting pairs over one set of said contacts and between. the other trunk and the other link over` another set of said contacts, subscribers lines ter-^ minating in said switch, two separate sets of contacts in said switch for each subscribers line for connecting it to one or the other of an associatedv pair of links, and means responsive to the seizure of a subscribers line for choosing a rst pair of trunks of which one atleast isv idle, for choosing a first trunk of said pair, if idle, and connecting said idle trunk to the associated link of the pair to which the calling line has access, over the contacts at the corresponding crosspoint, and connecting said link to the calling line over the corresponding separate. set of contacts.

2, In a telephone system, a crossbar switch` having intersecting horizontal and vertical rows of contacts, pairs of trunks, each pair terminating in a separate horizontal row of contacts, pairs of links, each pair terminating in a separate vertical row of contacts, a select magnet for each row of horizontal contacts, a hold magnet for each row of vertical contacts, means responsive tothe actuation of any select magnet followed by the actuation of any hold magnet for establishing a connection between the associated pair of trunks and pair of links over the contacts at the intersection of the associated horizontal and vertical rows of contacts, subscribers lines terminating in said switch, two separate sets of contacts for each subscribers line for connecting it to one or the other of an associated pair of links, a select magnet for one set of contacts as.- sociated with each subscribers line and one link in each pair, a select magnet for the other set of contacts associated with each subscribers line and the other link in each pair, means responsive to the actuation of either of said last-mentioned two select magnets and any hold magnet for establishing a connection between the associated subscribers line and the associated link over the corresponding set of contacts, means responsive to the seizure of a subscribers line for actuating the select magnet for a rst pair of trunks one of which at least is idle, for actuating the select magnet for the link having access to a first idle trunk of said rst pair, and means responsive to the actuation of said select magnet for said, first pairy of trunks for actuating the hold magnet for the links associated with the calling subscribersy line for establishing a connection between said subscriber's line, said link and said idle trunk.

3. In a telephone system, a crossbar switch having contacts arranged in horizontal andl vertical rows and select magnets and hold magnets for establishing connections between contacts andv intersecting rows, outgoing trunks terminating in: pairsv in contacts of individual horizontal rows, incoming trunks terminating in pairs in contactsv of individual horizontal rows, links terminating in pairs in. contacts of individual vertical rows, subscribers lines each terminating in one set of contacts in one horizontal level in position to connect with the contacts of one link of a pair and terminating in another set of contacts in another horizontal level in position to connect. with the contacts of the other link of said pair. means responsive to the seizure of a4 subscribers line for actuating two select magnets and one hold magnet for establishing a connection. between said subscribers line, one ofy the associated links. and. a. first idle trunk. ot a rst pair in which at least one trunk isy idle, and means for seizing a particular incoming trunk and actuating twoselect magnetsl and one hold magnet for establishing a connection between said incoming trunk, a particular link of the pair associated with a particular subscribers line and connecting said link with. said particular subscribers l-ine.

4. In a telephone system, a crossbar switch having contacts arranged in horizontal and vertical rows and select magnets and hold magnets for establishing connections between contacts at intersecting rows, trunks terminating in pairs in contacts of individual horizontal rows, links terminating in pairs incontacts of individual vertical rows, subscribers lines each terminating in one set of contacts in one horizontal level in position to connect with the contacts of one link of a pair and terminating in another set of contacts in another horizontal level in position to connect with the contacts of the other link oi said pair, and means responsive to the seizure oi a subscribers line for actuating two select magnets and one hold magnet for establishing a connection between said subscribers line, one of the associated links and a first idle trunk of a rst pair in which at least one trunk is idle.

5. In a telephone system, a plurality of crossbar switches, each having contacts arranged in. horizontal and vertical rows and select magnets and hold magnets for establishing connections between contacts of intersecting rows, trunks terminating in pairs of contacts of individual horizontal rows in one or more of said crossbar switches, links individual to each crossbar switch terminating in pairs of contacts of individual vertical rows in said switch, subscribers lines individual to each crossbar switch, each subscribers line terminating Iin one set of contacts in one horizontal level in position to connect with the contacts of one link of a pair and terminating in another set of contacts in another horizontal level in position to connect with the contacts of the other link of said pair, means responsive to the seizure of a subscribers line in any switch for actuating two select magnets and one hold magnet for establishing a connection between said subscribers line, one of the associated links and a first idle trunk of a ilrst pair in which at least one trunk is idle.

6. In a telephone system, a crossbar switch having contacts arranged in horizontal and vertical rows and select magnets and hold magnets for establishing connections between contacts of intersecting rows, trunks terminating in pairs in contacts of individual horizontal rows, links terminating in pairs in contacts of individual vertical rows, subscribers lilies each terminating in one set of contacts in one horizontal level in position to connect with the contacts of one link of a pair and terminating in another set of contacts in another horizontal level in position to connect the contacts of the. other link of said pair, means responsive to the seizure of a subscribers line for choosing and actuating the select magnet for a rst pair of trunks of which one at. least is idle and for simultaneously choosing and actuating the select magnet for the link having access to the first idle trunk of said iirst pair and for actuating the hold magnet for the links associated with the calling subscribers' line for establishing a connection from said call-- ing subscribers line over the chosen link and.' said chosenl idle trunk..

7. In a telephone system, a crossbar switch having contacts arranged in horizontal and vertical rows and select magnets and hold magnets for establishing connections between contacts at intersecting rows, trunks terminating in pairs in contacts of individual horizontal rows, links terminating in pairs in contacts of individual vertical rows, subscribers lines each terminating in one set of contacts in one horizontal level in position to connect with the contacts of one link of a pair and terminating in another set of contacts and another horizontal level in position to connect with the contacts of the other link of said pair, means including a busy test relay for each trunk responsive to the seizure of a subscribers line for choosing and actuating the select magnet for a rst pair of trunks of which one at least is idle as determined by the idle condition of the associated busy test relay and for simultaneously choosing and actuating the select magnet for the link having access to the first idle trunk of said first pair as determined by the idle condition of said associated busy test relay and for then actuating in response to the operation of said first select magnet the hold magnet for the links associated with the calling subscribers line, and means responsive to the operation oi' said select magnets and hold magnets for establishing a connection from said calling subscribers line over the chosen link and over the chosen idle trunk.

KENNETH L. FREDERICK. 

